In the related art, there has been known a method of supplying etching gas to a wafer accommodated in a processing container, and selectively etching a silicon film formed on the wafer. For example, a gas including a halogen element such as fluorine (F) or bromine (Br) is used as the etching gas from the view point that a silicon film can be removed with a highly volatile halogen compound (see, for example, Japanese Patent Laid-Open Publication No. 2002-118100).
In a case in which the silicon film is etched using a gas containing fluorine, end point detection may be performed by monitoring the amount of SiF4, which is a halogen compound produced by the etching, using a non-dispersive infrared (NDIR) sensor or the like (see, for example, Japanese Patent Laid-Open Publication No. 2012-151356).